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+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef RTC_BASE_TASK_QUEUE_H_
+#define RTC_BASE_TASK_QUEUE_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <utility>
+
+#include "absl/functional/any_invocable.h"
+#include "absl/memory/memory.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/task_queue/task_queue_factory.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/thread_annotations.h"
+
+namespace rtc {
+// Implements a task queue that asynchronously executes tasks in a way that
+// guarantees that they're executed in FIFO order and that tasks never overlap.
+// Tasks may always execute on the same worker thread and they may not.
+// To DCHECK that tasks are executing on a known task queue, use IsCurrent().
+//
+// Here are some usage examples:
+//
+//   1) Asynchronously running a lambda:
+//
+//     class MyClass {
+//       ...
+//       TaskQueue queue_("MyQueue");
+//     };
+//
+//     void MyClass::StartWork() {
+//       queue_.PostTask([]() { Work(); });
+//     ...
+//
+//   2) Posting a custom task on a timer.  The task posts itself again after
+//      every running:
+//
+//     class TimerTask : public QueuedTask {
+//      public:
+//       TimerTask() {}
+//      private:
+//       bool Run() override {
+//         ++count_;
+//         TaskQueueBase::Current()->PostDelayedTask(
+//             absl::WrapUnique(this), 1000);
+//         // Ownership has been transferred to the next occurance,
+//         // so return false to prevent from being deleted now.
+//         return false;
+//       }
+//       int count_ = 0;
+//     };
+//     ...
+//     queue_.PostDelayedTask(std::make_unique<TimerTask>(), 1000);
+//
+// For more examples, see task_queue_unittests.cc.
+//
+// A note on destruction:
+//
+// When a TaskQueue is deleted, pending tasks will not be executed but they will
+// be deleted.  The deletion of tasks may happen asynchronously after the
+// TaskQueue itself has been deleted or it may happen synchronously while the
+// TaskQueue instance is being deleted.  This may vary from one OS to the next
+// so assumptions about lifetimes of pending tasks should not be made.
+class RTC_LOCKABLE RTC_EXPORT TaskQueue {
+ public:
+  // TaskQueue priority levels. On some platforms these will map to thread
+  // priorities, on others such as Mac and iOS, GCD queue priorities.
+  using Priority = ::webrtc::TaskQueueFactory::Priority;
+
+  explicit TaskQueue(std::unique_ptr<webrtc::TaskQueueBase,
+                                     webrtc::TaskQueueDeleter> task_queue);
+  ~TaskQueue();
+
+  TaskQueue(const TaskQueue&) = delete;
+  TaskQueue& operator=(const TaskQueue&) = delete;
+
+  // Used for DCHECKing the current queue.
+  bool IsCurrent() const;
+
+  // Returns non-owning pointer to the task queue implementation.
+  webrtc::TaskQueueBase* Get() { return impl_; }
+
+  // TODO(tommi): For better debuggability, implement RTC_FROM_HERE.
+  void PostTask(absl::AnyInvocable<void() &&> task) {
+    impl_->PostTask(std::move(task));
+  }
+  void PostDelayedTask(absl::AnyInvocable<void() &&> task,
+                       webrtc::TimeDelta delay) {
+    impl_->PostDelayedTask(std::move(task), delay);
+  }
+  void PostDelayedHighPrecisionTask(absl::AnyInvocable<void() &&> task,
+                                    webrtc::TimeDelta delay) {
+    impl_->PostDelayedHighPrecisionTask(std::move(task), delay);
+  }
+
+ private:
+  webrtc::TaskQueueBase* const impl_;
+};
+
+}  // namespace rtc
+
+#endif  // RTC_BASE_TASK_QUEUE_H_